Cylinder head gaskets made with layers of facing material have been manufactured and used for decades. Such gaskets usually employ fire rings, such as U-shaped armors with or without wires, at the combustion openings to embrace the peripheral edges defining the combustion openings, thereby to protect the edges and enhance the sealing effect thereat.
Sometimes the armors have been integrated so that the armors for pairs of adjacent or adjoining combustion openings comprise a unitary assembly. In some instances one entire surface of the gasket is covered with the sheet material from which the armors are formed.
The presence of integrating material at the zones of adjacency of pairs of combustion openings enhances the seal thereat, particularly where the combustion openings are very close to each other and the facing material is therefore weakened and fragile.
Various sealing adjuncts have been provided for use at conventionally armored combustion openings and especially for use in the zones of adjacency of pairs of such openings. Thus, for example, multiple armors have been employed, with a second U-shaped armor simply overlying a first U-shaped armor. This, of course, enhances the seal to be effected thereat. In other instances metal shims have been placed under a leg of the U-shaped armor to provide for greater sealing stress. In some such cases, the shims for adjacent combustion openings are formed with, hence integrated with the armors in the zone of adjacency of a pair of combustion openings, thereby to enhance the sealing effect and to protect the facing layer or layers thereat.
While all of these armoring techniques and adjuncts are of advantage, none is ideal. All of them tend to be sensitive to the conditions and loads at the combustion openings, such as excessive loads due to thermal push, and tend to permit extrusion of facing layers when the gasket is exposed to excessive clamp loads, such as because of thermal push. This tendency is most severe in the zones of adjacency of pairs of adjacent combustion openings.
It would be of advantage to provide improved armoring and a method of making a gasket providing such improved armoring.